Application of singularity theory to cascade design

It is well recognized that the variation of axial velocity in a cascade has an important effect on its performance. Formulas predicting the effect of Axial Velocity Ratio (AVR) on the aerodynamic parameters are very useful to improve design accuracy when using NACA cascade data. This paper suggests a singularity approach to investigating this effect of AVR on the cascade performance. Based on Schlichting theory, a virtual-equivalent velocity diagram is incorporated. By embedding velocity fields with singularities, the flow angle, equivalent diffusion ratio, momentum thickness, and total pressure loss coefficient are calculated. A numerical example is given, which shows a good agreement with experimental data. Furthermore, an improved design procedure under the condition of AVR≠1 is also proposed, which has been applied to design for a diagonal flow blower in this paper.